1. Technical Field
The invention relates to optical elements, and particularly to a lens module.
2. Description of Related Art
Currently, with the development of electronic devices providing multiple functions, camera modules have become widely used in a variety of consumer electronic devices such as notebook computers, personal digital assistants (PDAs), cellular phones, and others. There is a corresponding increase in the demand for improved image quality, which essentially depends on the quality of a lens module of the camera module.
Generally, a lens module of a camera module has an opening defined at one end thereof, which allows light to enter. The light passes through a plurality of lenses inside the lens module and then converges on a sensor, such as a charge coupled device (CCD), which generates an image. Due to different distances from a subject to the lens module, angles of incidence of the incoming light vary correspondingly. Because luminous flux is inversely proportional to the angles of incidence, thus uneven brightness of the image will be generated. That is, brightness at the periphery area of the image is reduced as compared with that at the central area.
What is needed, therefore, is a lens module providing even brightness distribution.